The International Cessna^® 170 Association

Where is a good source (inexpensive) for a master solenoid. $450.00 from Cessna sounds rather spendy

Joe
4518C

This one works great:
http://www.aircraftspruce.com/catalog/e ... rrelay.php

The parts manual calls for p/n 0411021-1. When that one is no longer in stock use p/n 0712603-1. Entering that p/n into Iwantcessnaparts comes up with it being superceded to p/n 0712603-2 for $426.55. But a look at Cessna Service Letter 65-89 says, "An improved design heavy duty battery contactor has been incorporated on all 1966 single engine models. ... this same contactor can be addded to all earlier single engine models." They say to use S1579-1 which has been superceded by S1579A2 which has been superceded by p/n 111-140D which is available for $42.08 at cessnaparts.com. Don't forget to install diode p/n 0770728-1 on the relay. It only costs $44.56! My guess is the aviation division at Radio Shack might have it a bit cheaper.

For further information also see http://www.cessna120-140.org/forum/file ... pulses.pdf
and http://www.cessna120-140.org/forum/file ... noid_2.pdf

Edit on 02/24/15: SEL 24-02 lists the latest master solenoid / relay / contactor as p/n P52-0034-1.

Any NAPA auto parts store should have a "Continuous" 12v solenoid that works fine. When checking to see if it is the correct type for the job,look for electrical continuity between the small terminal and the large input terminal from the battery. A master switch solenoid should "Make" when connected to the battery and the small terminal is connected to ground.
And it sure as hell shouldn't cost anything like those prices quoted. Maybe $15 or $20.

Thanks guys, I can buy a lot of gas for $450.00, well, maybe not a lot...

Joe

If you use a NAPA part (or other auto part) be CERTAIN that the one you select is intended for CONTINUOUS DUTY and not intermittent duty. (Those intended for starter operations are intermittent only and will overheat in continuous use such as in the battery master switch operation of our aircraft.)

I sometimes see this type part on sale at EBAY.

Sometimes it is NOS, NIB , used and sometimes you may purchase a defective part. So bid accordingly.

Many mechanics , owners etc are cleaning out man treasures that they just never got around to using.

Regards

FORGET e-junk on this inexpensive part. New, aircraft quality, correct part is less than $18 from Spruce. 877-477-7823

It would be a good time to add a diode. You should have one on the master solenoid and one on a
Key type starters solenoid.

http://www.cessna120-140.org/forum/file ... pulses.pdf

http://www.aircraftspruce.com/catalog/e ... idassy.php

gahorn wrote:FORGET e-junk on this inexpensive part. New, aircraft quality, correct part is less than $18 from Spruce. 877-477-7823

Yes, and by the way the bracket holes line up perfectly with previous mounting holes.

Great info, thanks! I have an 0-300 with a key start so I'll put a diode on both solenoids.

Joe

Here's a recent Cessna video showing why one needs a diode on a solenoid.

Gary,
Is there a way to view this video without having to sign up with Cessna?

John,
Give me a minute, I'll look for another link. ... There. Fixed the link. Thanks for bringing it to my attention. I was logged into Cessna Support and didn't realize the video couldn't be viewed without logging in.

Cool video. Diodes anyone?